Histology Flashcards
What are the 4 major type of cells found in the Epidermis
Keratinocytes
Melanocytes
Intraepidermal macrophages
Tactile epithelial cells
Mutation of keratin 5 and 14 is the cause of what disease
Epidermolysis bullosa simplex
Mutation of karatin 1 and 10 is the cause of…
Epidermolytic hyperkeratosis
Defects of keratin 2e cause…
ichthyosis bullosa of siemens
Defects of keratin 09 is associated with…
Epidermolytic palmoplanter keratoderma
Cacitriol hormonal actions
Increases calcium absorption from the gut
Increases calcium reabsorption from the kidney
Increases bone mineralisation
Vitamin D receptor binding apoptosis
Function of MITF
Lack of MITF leads to what disorder
Excess of MITF leads to what disorder
Functions to regulate melanocyte differentiation
.Albinism
.Melanoma
Mutation in the gene for tyrosinase leads to what?
leads to less melanin
leading to albinism
What is Vitiligo
- Autoimmune loss of melanocytes - white patches on
otherwise normal skin - Largely a cosmetic issue
- Some individuals pursue complete depigmentation of skin to
generate a uniform skin colour
function of unencapsulated nerve endings
Mediate PAIN, TEMPERATURE, non-discriminative touch(Crude touch (or non-discriminative touch) is a sensory modality that allows the subject to sense that something has touched them, without being able to localize where they were touched (contrasting “fine touch”).)
Functions of Apical Dark cells inMerocrine sweat glands
Secrete glycoproteins by exocytosis(merocrine secretion)
Function of Basal clear cells
Secrete water and electrolytes into the intercellular canaliculi
What type of a genetic disorder is cystic fibrosis and in what gene does the mutation occur leading to disorder
Genetic autosomal recessive disorder - Mutation in the CFTR gene (Cystic
Fibrosis Transmembrane conductance Regulator), affects epithelial
transport of Cl
Compare and Contrast Na+ and Cl- transport in normal sweat duct and Na+ and Cl- transport in sweat duct of CF sufferer
Na+ and Cl- transport in normal sweat duct
As primary sweat moves along the duct most of
the NaCl is reabsorbed.
* This is driven by a large inward gradient for Na+,
which flows into the cell through epithelial Na+
channels (ENaC) in the apical membrane.
* This Na is then transported out of the cell and
into the blood via the basolateral sodium pump
(Na+/K+ ATPase).
* Because Cl- is electrically attracted to Na+, it
follows it by flowing through the CFTR Clchannels
* The result is the production of dilute sweat, so
that we can be cooled by evaporation without
losing an undue amount of salt.
Na+ and Cl- transport in sweat duct of CF sufferer
* In CF sweat ducts, Cl- conductance is
completely abolished because of
defective CFTR.
* When Na+ attempts to flow out of a CF
duct through remaining sodiumselective pathways, it is unaccompanied
by Cl-.
* This creates an excess of negative
charge in the duct which attracts Na+
and prevents its further absorption.
* Therefore very little NaCl is
reabsorbed, resulting in a high salt
content (>100 mM vs. typical values of
20-30 mM in healthy individuals) in CF
sweat.
* The sweat chloride concentration is
the most reliable single physiological
marker of CF.
What are the functions of the skin
Thermoregulation, Protection (mechanical and against microorganisms), Water barrier, Cutaneous sensations, Excretion and absorption, Synthesis of Vitamin D.
What are the three major layers of the skin
Epidermis, Dermis, Subcutaneous (hypodermis) layer.
Describe the structure of the epidermis
Comprised of multiple layers of cells, including keratinocytes, melanocytes, intraepidermal macrophages (Langerhans cells), and tactile epithelial cells.
What is the main function of keratinocytes?
Keratinocytes protect the skin and underlying tissues from abrasions and heat, contribute to wound healing, and produce a water-repellent sealant to reduce water loss and protect against foreign materials.
How do keratinocytes mature through the epidermis, and how is the epidermal permeability barrier formed?
Keratinocytes mature from the basal layer to the superficial layer over a 3-4 week period, undergoing characteristic changes and filling with keratin. The epidermal permeability barrier is formed through the production of multi-lamellar lipids, cornified cell envelope, and the keratin-filaggrin complex.
hat are the types of junctions between skin cells, and what are their functions?
Tight junctions, adherens junctions, desmosomes, and hemidesmosomes. They contribute to cell-cell communication, adhesion, and stability, forming barriers and anchoring points.
How is Vitamin D3 produced, and why is it important?
Vitamin D3 is synthesized in the skin through UV exposure, essential for normal absorption of calcium and phosphorus from the intestine, and crucial for various physiological functions including immune function.
Explain the process of melanin synthesis by melanocytes.
Melanocytes produce melanin, which protects the skin from UV damage. The synthesis pathway involves the conversion of phenylalanine to tyrosine, oxidation of tyrosine to DOPA, and further reactions leading to the production of either eumelanin or pheomelanin.
How do Langerhans cells contribute to immunity in the skin?
Langerhans cells, also known as intraepidermal macrophages, recognize and present antigens to the immune system, perform phagocytosis, and play roles in allergy and chronic skin inflammation.
What are the different types of sensory receptors in the skin, and what do they detect?
Merkel receptors, Meissner corpuscles, Ruffini cylinders, Pacinian corpuscles, and free nerve endings. They detect pressure, touch, vibration, and temperature changes.
